I don't see how Trump can fire Mueller.
Yes, there are compelling reasons for doing so. To a person, everybody on Mueller's 14-person staff is a Democrat who has contributed to Dem campaigns. The scope of the investigation is already metastasizing. The investigation is serving as a distraction from the far more plainly discernible Russian connections of the Clinton machine, not to mention as a distraction from the agenda that Republicans would like to pursue.
But there is an undeniable stench wafting off Trump's own maneuvers throughout all this. As David French at NRO has reminded us, it was questionable Russia dealings that led to the departure of a campaign chair, national-security adviser and foreign-policy adviser. Then there is the meeting in the Oval Office with Kislyak in which, in his signature style, Trump bragged about firing Comey and called him a "nut-job" - and shared classified information. Of course, there is also the "I'd love that!" line in Jared Kushner's email exchange with Rob Goldman.
Another NRO piece on this, by Andrew McCarthy, shows that Assistant AG Rosenstein, in order to burnish his impartiality bona fides, gave Mueller a free reign in the investigation's scope that Justice Department regulations don't actually allow him to grant. You think Capitol-Hill Dems had any interest in bringing that up with him?
Then there is the latest tweet flurry from DJT himself, full of whining ("It's very sad that Republicans, even some that were carried over the line on my back, do very little to protect their President.") and gloating ("As the phony Russian Witch Hunt continues, two groups are laughing at this excuse for a lost election taking hold, Democrats and Russians!"). This is not the alpha-male behavior that DJT's slavish devotees think he exhibits.
So, while there's validity to the witch-hunt view of this, there's also the recklessness factor.
To just say, "Can Mueller and let's get on with the agenda the American people want from our government!" is to gloss over too many actual questionable developments, developments that stem from the fact that we elected as president someone unfit for the office.